A method of manufacturing magnetic heads comprises the step of: fabricating a magnetic head substructure by forming components of a plurality of magnetic heads on a single substrate, wherein a plurality of rows of pre-head portions that will be the respective magnetic heads later are aligned in the substructure; and fabricating the magnetic heads by separating the pre-head portions from one another through cutting the substructure. In the substructure first resistor elements and second resistor elements are formed. Each of the first resistor elements has a resistance that varies depending on the location of an end of an MR element located in a medium facing surface along the direction orthogonal to the medium facing surface. Each of the second resistor elements has a resistance that varies depending on the location of an end face of a track width defining portion located in the medium facing surface along the direction orthogonal to the medium facing surface. The medium facing surfaces are formed while monitoring the resistance values of the first and second resistor elements.